But what makes it absolutely watchable is a breakout performance by Oscar Isaac, who gets his first starring role after toiling around in supporting parts for years.

He plays the titular Llewyn (pronounced LU-win) Davis, and the film follows him for a week in his life as he tries to navigate the burgeoning folk music scene of Greenwich Village in 1961.

The film opens with him performing on stage at a small nightclub. He’s clearly in his element, and his singing will induce chills. He’s vibrant, full of energy and life.

But then he stops singing, and that’s when everything goes wrong, starting with getting punched in the face in a dark alley.

For Llewyn is clearly a mess. He ambles from free bed to free couch, crashing wherever he can, not minding to impose. He’s self-centered. Rude. Self-serving.

After crashing at a friend’s swanky apartment, he accidentally lets the tenant’s cat out just as the door’s closing and he doesn’t have a key. Great. Now he has to lug a cat and his guitar around with him everywhere he goes. Life’s just not fair!

So he drops in to see friends Jim (Justin Timberlake) and Jean (Carey Mulligan), only to find that Jean has promised their couch to a fellow musician, Troy Nelson (a gamely naive Stark Sands). It’s there that Jean delivers some startling news to Llewyn.

And this propels his journey of self-destruction.

After wearing his welcome out with Jean, Llewyn takes to the road, hitch-hiking in hopes of auditioning for record producer Bud Grossman (a wonderfully stoic F. Murray Abraham) in Chicago. He gets picked up by a jazz musician (John Goodman) and his driver sidekick (a chain-smoking, street-cool Garrett Hedlund, from “Tron: Legacy”).

But things don’t go well for Llewyn. So much so that he ponders giving up his dream of playing music. Despair and frustration set in. The guy just can’t seem to get a break.

Not that he deserves one, really, the way he treats people. What’s worse is that he knows he’s being a jerk. He just keeps doing it, although his conscience eats at him later.

But even when he’s being temperamental or surly, we still somehow root for him.

Part of the reason for that is the humor in the Coens’ script. They’ve made Llewyn insufferable but also darkly funny. And that somehow makes him sympathetic.

Part of that, also, is the film’s glorious music. All the musicians performed their music live for the camera, and Isaac is a mesmerizing performer, with a voice that is intimate, tender yet scruffy. The film’s music is almost a character unto itself, much as it was in the Coens’ “O Brother, Where Art Thou?”

Loosely based on Dave Van Ronk’s memoir “The Mayor of MacDougal Street,” the film is set in an era that was still trying to establish itself. Folk music hadn’t hit its stride yet with the arrival of Bob Dylan. It was also just coming off the age of the rock ’n’ roll ’50s.

In that vein, Llewyn is still trying to establish himself, as well. What’s interesting is that while the film is titled “Inside Llewyn Davis” (so is the character’s record album in the film) Llewyn himself makes it a point not to let anyone “inside.” He’s carefully guarded. But we can see that he’s also vulnerable.

The Coens skip most of their usual filmmaking quirks here, going for a tonal exploration rather than a plotted story. It’s a more modest, less-aware approach that suits the film well.

Eventually, “Inside Llewyn Davis” emerges as a profound meditation on how we’re all looking to find our place.